Investigation of the Mosquito Abatement and Vector Control District




In the early 1980s, citizens of Supervisorial Districts 2 and 4 were logging complaints to the Board of Supervisors about the annoying mosquito problem. In 1983, the Board of Supervisors established the Mosquito Abatement and Vector Control District (MAVCD). Supervisorial Districts 1, 3, and 5 did not have the same difficulty and were not included in the MAVCD.


The MAVCD investigates complaints by locating the breeding ground of the mosquito infestation and eliminating it. The MAVCD is funded through a property tax assessment to properties in the district. Its services are free to the public. People who live outside the district must contact a private company and pay for these services.


There are fifteen different types of mosquitoes in the County of Santa Cruz and three are known carriers of the West Nile Virus. The MAVCD monitors several sites near known mosquito breeding grounds. The MAVCD lays traps and counts the type and number of mosquitoes in each trap. The MAVCD freezes the trapped mosquitoes and sends them to the state Viral and Rickettsial Disease Laboratory (VRDL) at UC Davis for analysis. A second method of monitoring is done by taking blood samples twice a month from a flock of chickens located at Watsonville High School, which is located in the MAVCD. The high school was chosen for the site of the chickens for two reasons. The first is because the school is located between several bodies of water (the sloughs and Pinto Lake). The second reason is that the chickens are used as an educational tool for the students at the high school. The samples are submitted to the state VRDL and analyzed for traces of infectious diseases including the West Nile Virus. These monitoring methods alert the county to increases in the mosquito population and potential health threats.


To control the mosquito population, the Mosquito Abatement and Vector Control District:



Larvicides prevent the mosquitoes from developing beyond the adolescent stage, before they are capable of breeding. Microbials and analogs are not hazardous to humans and wildlife. Oils are potentially harmful to fish and other aquatic organisms and are not used in environmentally sensitive areas. The MAVCD is responsible for not altering the ecological balance. The use of larvicides allows birds, lizards, and other creatures to continue to feed on the mosquitoes.


The Mosquito Abatement and Vector Control District is responsible for locating, monitoring, and controlling the mosquito population in Supervisorial Districts 2 and 4, the southern part of the county, primarily to prevent the spread of disease. The West Nile Virus was first detected on the east coast of the United States in 1999. As of January 2003, the virus has killed 259 humans, hundreds of birds, and an unknown quantity of other animals such as horses in the United States of America. The MAVCD, Santa Cruz health officials, and the Center for Disease Control (CDC) expect the West Nile Virus to spread throughout the entire county by the end of 2003. Although the West Nile Virus is a cause of consternation for health officials in Santa Cruz, malaria and encephalitis pose greater threats to public health.




Concerns over the West Nile Virus led the 2002-2003 Grand Jury to investigate the Mosquito Abatement and Vector Control District. The Grand Jury investigation included:


        how the district monitors the mosquito population

        the extent of the threat posed by the West Nile Virus

        whether the district should be expanded to cover the entire county




The Grand Jury interviewed personnel from the MAVCD, the County Department of Environmental Health Services, the County Department of Agriculture, and people who have used the services of the MAVCD. The committee reviewed the 1999-2000 Biennial Report of the Santa Cruz County Mosquito Abatement and Vector Control District. The committee also reviewed the following websites:





  1. The purpose of the MAVCD is to monitor breeding grounds, regulate the mosquito population, and control the spread of mosquito borne disease. The district carries out these duties by:


a) conducting various educational programs

b) monitoring known breeding grounds

c) sending frozen mosquitoes to UC Davis for testing

d) sending chicken blood samples to the VDRL state lab for disease testing

e)      applying larvicides and distributing mosquito eating fish


Response: Santa Cruz County Board of Supervisors AGREES


The District does not routinely send mosquitoes to an outside lab for testing, but would do so in the event of mosquito-borne disease found in the County. Besides the use of larvicides and fish, the program controls mosquitoes through other Integrated Pest Management measures such as property-owner education and source reduction.


2.      West Nile Virus and other forms of mosquito borne diseases are a threat to all of Santa Cruz County according to the CDC and Santa Cruz health officials.


Response: Santa Cruz County Board of Supervisors AGREES


  1. The south portion of the county, Supervisorial Districts 2 and 4, is currently included in the MAVCD.


Response: Santa Cruz County Board of Supervisors AGREES


  1. The MAVCD is funded by a property tax assessment.


Response: Santa Cruz County Board of Supervisors AGREES


  1. The cost of extending the MAVCD to the unincorporated areas of Supervisorial Districts 1, 3, and 5 is expected to be $340,000 the first year to increase the staff from 3 to 6 and to purchase new equipment. The annual future cost is estimated to be $270,000.


Response: Santa Cruz County Board of Supervisors AGREES


  1. The combined cost for the three cities (Capitola, Santa Cruz, and Scotts Valley) not currently covered by the MAVCD should be approximately $220,000 a year.


Response: Santa Cruz County Board of Supervisors AGREES


The County agrees with this finding, with the following clarification. This cost of extending the district is estimated to range from $130,000 to $220,000. Staffing needs would depend on type of services requested: mosquito operations only with advice on other vectors, as is current practice, or with other vector services such as rodent and yellowjacket control.


  1. The cost to cover all of Santa Cruz County (unincorporated areas and the cities) as of March 17, 2003 will be paid by an estimated property tax assessment of $8 to $10 per parcel.


Response: Santa Cruz County Board of Supervisors PARTIALLY AGREES


Since the last analysis of estimated costs per parcel for a countywide program, upon which the Grand Jury finding was based, actual program operating costs have increased and the revised estimated per parcel charge is $10 - $11.50. This is an approximate range; actual costs, of course, may vary depending on cost efficiencies from serving large areas and the level of service required for certain parts of the County.




1. The MAVCD is doing an outstanding job of controlling potentially deadly pests in the southern portion of the county.


2. Extending the district to the entire county would benefit the northern portion of the county.




  1. The Board of Supervisors should extend the Mosquito Abatement and Vector Control District to the entire county.


Response: Santa Cruz County Board of Supervisors


Steps are being taken to determine feasibility of implementation. The County has hired a consultant to conduct a public opinion survey to measure property owner support for possible expansion. This survey has been implemented, and the results, analysis and recommendations will be reported to the Board of Supervisors in September. The County will also contact the City of Santa Cruz, City of Scotts Valley and the City of Capitola to inform them of the survey findings and determine their interest in possible annexation to the District. Further steps would depend on the outcome of the survey and may result in a decision to proceed with a ballot measure in all or some parts of the County.


Responses Required





Respond Within

Santa Cruz County

Board of Supervisors



60 Days

(Sept. 2, 2003)